in my experience that's not the case; i stand on a lower platform in complete darkness (green LED and all), fire a bolt above at a guy also patrolling in complete darkness save for glow of his flashlight in an unrelated direction, and someone, somewhere is gonna see or hear that guy fall, and the entire base is gonna come and kill me w/ kalashes
if they do come my way, regardless of their actual intentions to slaughter me with a kalash, they /WILL/ see me through complete darkness and open fire. my only hope is to snipe them while they're trying to notice me, which is really freaking hard because the back of the level doesn't have a faint glow, unlike some of the very bottom
even when i do manage to clear out the entire lower level and one of the upper level enemies without attracting any attention (only happened once, when i got the goggles) there's a cluster of enemies near the front of the bridge that i have to get past, and i don't see any way of killing one without the others noticing